The present invention relates to swing-type actuators for positioning read/write heads in memory storage devices and, more particularly, to an improved swing-type actuator constructed partially from plastic.
Numerous swing-type actuators are known in the prior art. Representative examples include those shown in U.S. Pat. No. 4,985,652 to Oudet, et al. and U.S. Pat. No. 4,916,456 to Manzke, et al. Such devices typically include a coil secured to one or more longitudinally extending arms. If more than one arm is utilized, the plurality of arms is known as an "E-block". A read/write head is typically attached to each arm on the end opposite the coil. The actuator is pivotally secured about a shaft such that the read/write head is positioned adjacent a data disk and the coil is placed in a magnetic field by, for example, positioning it adjacent one or more permanent magnets. Current is supplied to the coil, thereby generating an electromagnetic force and causing movement of the coil within the preexisting magnetic field. Correspondingly, the arms pivot about the shaft to move the read/write heads to selected locations adjacent the disk.
In some embodiments of the above-described swing-type actuator, the arm is constructed from metal, such as aluminum. Metal arms have several advantages, including the ability to more readily and securely attach read/write heads to the arm, the ability to maintain exacting tolerances for the arm, and the relative ability to more easily machine features into the arm. The coil is typically attached to metal arms by means of screws, similar fasteners or adhesives. However, for various reasons, including ease of manufacturing, it has been found desirable to secure the coil to the arm by injection molding thermoplastic material around a portion of the coil and a portion of the arm. Examples of such actuators include U.S. Pat. No. 5,122,703 to Takahashi, et al., as well as numerous earlier actuators manufactured by the assignee of the present application.
Although the above-described actuators are all acceptable for their intended uses, they do have certain undesirable features. For example, an aluminum E-block can be relatively expensive to manufacture. Additionally, it may be desirable to provide an actuator having a lower overall weight than one utilizing an aluminum E-block, thereby reducing inertia and momentum and the attendant forces necessary to move and stop the actuator. Accordingly, all-plastic actuators have been proposed. In such actuators, the coil is placed in a mold and the actuator arm is simultaneously formed from a thermoplastic material and molded to the coil. Examples of such actuators include U.S. Pat. No. 5,165,090 to Takahashi, et al., as well as earlier actuators manufactured by the assignee of the present application.
Although all-plastic actuators may be suitable for their intended purpose, they lack some of the more desirable properties of actuators having metal arms. For example, it has been determined that the read/write head may be more easily and readily attached to a metal component than a plastic one. Similarly, it may be easier to machine features into metal than plastic.
Accordingly, it is an object of the present invention to provide an improved swing-type actuator for carrying a read/write head.
Another object of the present invention is the provision of a swing-type actuator that is lightweight and durable.
Yet another object of the present invention is the provision of a swing-type actuator that allows for easy and secure attachment of the read/write head to the actuator arm.
Another object of the present invention is the provision of a swing-type actuator that can have a read/write head secured thereto with a staking ball and eyelet combination.
Still another object of the present invention is the provision of a swing-type actuator having an arm capable of being machined to include desired features.
These and other objects of the present invention are attained by the provision of a swing-type actuator which comprises a coil, at least one arm formed from metal and having a first end and a second end, and a molded thermoplastic body which includes a journal disposed between the first end of the arm and the coil. The body is molded about a portion of the first end of the arm and at least a portion of the coil so as to secure the arm and coil to the body.
In one embodiment of the present invention, the arm is a stamping having a generally flat portion of uniform thickness and at least one flat surface on one edge thereof. The molded body surrounds a portion of the flat surface. One end of the arm includes a feature that cooperates with a portion of the body to secure the arm to the body, and the other end of the arm has a hole therein for attaching a read/write head to the arm. The arm includes at least one wire guide machined therein for receiving a wire which attaches to the read/write head.
In another embodiment of the present invention, the arm includes a hole therein for reducing the mass of the arm.
In another embodiment of the present invention, the actuator includes a bobbin having a body, a plurality of terminal pin sleeves having terminal pins disposed therein and a bridge member joining the body and the sleeves. The coil includes a plurality of lead wires attached to the terminal pins and the coil is disposed about the body of the bobbin.
According to yet another embodiment of the present invention, a swing-type actuator includes a coil, at least one arm and a molded thermoplastic body. The arm includes first and second ends and comprises a plastic portion and a metal mounting pad. The body has a first portion molded about a portion of the coil to join the coil to the body, and a second portion molded about the first end of the arm to join it to the body.
In still another embodiment of the present invention, the mounting pad includes a body portion, a securement portion for securing the mounting pad to the plastic portion and an attachment portion for attaching a read/write head to the mounting pad. The attachment portion includes a hole therein for attaching a read/write head to the mounting pad and has beveled edges for accommodating the tooling used to attach the read/write head to the mounting pad. Both the attachment portion and the securement portion extend generally perpendicularly from the body. The plastic portion surrounds the securement portion so as to secure the mounting pad to the plastic portion. Additionally, the plastic portion is electrically conductive.
According to another embodiment of the invention, the plastic portion of the arm includes at least one wire guide. The wire guide may take the form of staggered protrusions extending from the plastic portion.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.